I think we are going to wind up with some sort of 'thumbfriendly'.X.com. If that's 'handheld' or 'iphone' or 'mobile' doesn't really matter to me; nor does the excessive 'dumbing down' that mobile domains typically bring.

What I care about is layout and interface elements that don't assume individual pixel precision. The curse of most 'mobile' views is that they still assume a stylus. Stylii suck it. (along those lines, microb should consider making the 'hotspot' of links in the browser a bit larger, and easier to thumb.)

CSS by itself isn't enough.
The most important changes vis-a-vis a mobile 'look', is toning down excessive inline images, scripts, plugins and page size: not tasks that are properly achieved with css. (you can use CSS to hide such elements, but the browser will still download them) As 99% of the web is dynamically generated HTML these days, it's more appropriate for everyone if they simply add another rendering path in their code for alternate views.

The lack of proper support for alternate paths has more to do with lack of tangible ROI and penny-pinching development budgets: Mention gracefully-degrading versions of a site for various devices/browsers and watch a client's eyes glaze over. Invariably the script-free, lynx-friendly, mobile-friendly and ADA-compatible versions get cut.